You either take faith to 30 or take it to 50. At 30 faith you get your buffs and a decent mad adjust. The mag adjust gains from 30 to 40 are underwhelming at best. 40 to 50 is a substantial increase, but it's also a lot (20 levels) of investment for something like 30% more damage (from the 30 faith values) on WoG/buff damage. Lightning spear and it's relatives are completely unsuitable for PvP, even with 45 dex... I've honestly never seen anyone be hit by one and will typically shoot people with my bow if it starts getting used.
So I'd take faith to 30 and pump it into dex, this way your base damage probably grows as much as your buff damage shrinks and you'll have faster spell casts as well. The rest vit and end gouge accordingly... don't 16 int dark bead bro.